This invention relates to operators for fluid flow control devices, such as valves, for example. In particular, this invention relates to push-pull operators for air valves, for example of the type including a manually engageable button mounted on a plunger for controlling the position of the plunger and thus the operation of the valve.
U.S. Pat. No. 4,790,208 shows a knob and shaft assembly for operating, for example, a vehicle air brake control valve. The assembly includes a knob having a front face and a barrel projecting from the face, and a shaft which is threadedly engaged with threads on the barrel. The assembly is provided with locking detents comprising protrusions on the shaft which are received within apertures on the barrel to releasably lock the knob to the shaft, thereby preventing the parts from being accidentally becoming disengaged. This also assures the proper orientation of the knob with respect to the shaft to permit indicia embossed on the knob to be easily read by the operator.